A proton and an alpha particle (q = +2.00e, m = 4.00u ) are fired directly toward each other from far away, each with an initial speed of 0.202c. What is their distance of closest approach, as measured between their centers? (Hint: There are two conserved quantities. Make use of both.)

Question

anonymous · Answer

answer in the textbook is 4.71×10-17 m

anonymous · Answer

So do you know how to approach this?

anonymous · Answer

no idea :/

anonymous · Answer

Wait.. if this involves relativistic physics .. then i can't help, else its basic conservation principle!

anonymous · Answer

As the two particles move towards each other, what happens to their speeds?

anonymous · Answer

energy is conserved 
hmmm...as the two particles are close to each other im pretty sure the speed with be the same for both when they are close to each other but slower than the initial velocity?

anonymous · Answer

and this problem doesn't have to deal with relativity @Mashy

anonymous · Answer

well.. electric fields are conservative.. hence total mechanical energy is conserved.. 

when they come close and stop, all the initial k.E gets converted to p.E 
so can you develop an energy conservation equation??

total intial k.E = total final p.E